Alpha-numerical display device

ABSTRACT

An alpha-numerical display device comprising a plurality of light emitting diodes mounted in a prearranged design on a surface of a transparent plate whose diode mounting surface side has formed thereon a plurality of conductive strips between which a layer of opaque insulating material is formed except for windows in which the diodes are located. An insulating layer covers the opaque layer and the conductive strips. Bridging strips are formed in a layer overlying the insulating layer which connect the electrodes of the diodes to their associated conductive strips for energization. Each bridging strip extends at one end down through a window in the insulating layer adjacent an associated diode electrode into electrical contact therewith and the other end extends down through another window into electrical contact with its associated conductive strip. A reflective layer may be employed above the back side of the diode and spaced therefrom to cause the bulk of the light emitted from the diode to be transmitted through the transparent plate on the front side of the diode. A modified form of the structure may be had by using the conductive strips both as a mask and as a conductive member. This is accomplished by shaping the conductive strips so that while isolated from each other they still cover a very large percentage of the surface of the transparent mounting plate.

United States Patent [191 Usui [451 Oct. 8, 1974 1 ALPHA-NUMERICALDISPLAY DEVICE [75] Inventor: Setsuo Usui, Kanagawa-ken, Japan [73]Assignee: Sony Corporation, Tokyo, Japan [22] Filed: Jan. 3, 1973 [21]Appl. No.1 320,720

[30] Foreign Application Priority Data Primary Examiner-Harold l. PittsAttorney, Agent, or Firm-Hill, Gross, Simpson, Van Santen,SteadmamChiara & Simpson [57] ABSTRACT An alpha-numerical display devicecomprising a plurality of light emitting diodes mounted in a prearrangeddesign on a surface of a transparent plate whose diode mounting surfaceside has formed thereon a plurality of conductive strips between which alayer of opaque insulating material is formed except for windows inwhich the diodes are located. An insulating layer covers the opaquelayer and the conductive strips. Bridging strips are formed in a layeroverlying the insulating layer which connect the electrodes of thediodes to their associated conductive strips for energization. Eachbridging strip extends at one end down through a window in theinsulating layer adjacent an associated diode electrode into electricalcontact therewith and the other end extends down through another windowinto electrical contact with its associated conductive strip. Areflective layer may be employed above the back side of the diode andspaced therefrom to cause the bulk of the light emitted from the diodeto be transmitted through the ductive strips so that while isolated fromeach other they still cover a very large percentage of the surface ofthe transparent mounting plate.

14 Claims, 16 Drawing Figures PATENTED BET 1 74 3.840.858 SHEET 20F 4PATENTEBUBI 8:914

SHEET 3 0f 4 PAIENTEDBBT 81w 3 840 858 sum nor 4 I ALPHA-NUMERICALDISPLAY DEVICE CROSS-REFERENCES TO RELATED APPLICATION This applicationis related to co-pending application Ser. No. 384,232, filed July 31,1973, entitled AL- PHA-NUMERIC CHARACTER DISPLAY DEVICE AND METHOD,WHOSE CHARACTERS ARE FORMED OF LIGHT EMITTING DIODES," assigned to theassignee of the present application and in which the inventor is SetsuoUsui.

BACKGROUND OF THE INVENTION Alpha-numerical display devices have nowcome into rather extensive use. As the term is used, an alphanumericaldisplay refers to a grouping of individual segments which form anumeral, a letter or some other sign. Typically such devices are formedin a glass envelope containing an ionizable gas with the segments formedas cathode elements and with one or more anodes associated with a groupof cathodes'to cause the segments to glow. One disadvantage of this typeof device lies in the fact that it is difficult to get a sharp narrowline for each segment of the display.

Light emitting diodes are known. The emitted light from such a diodecomes from hole-electron recombinations. In a solid-state light-emittingdiode the supply of higher energy electrons is provided by forwardbiasing the diode, thus injecting electrons into the n region (and holesinto the p region). The injected holes and electrons then recombine withthe majority carriers near the junction. The recombination radiation isthen emitted in all directions.

Heretofore, one form of light emitting diode which has been used is asshown in FIG. 16 with one ohmic contact formed on one whole surface ofthe diode and other ohmic contact partially covering the surface of thediode. In such an arrangement, the utilized light is l numerical displaydevices, and one such structure is disclosed in Electronics, May

ll, 1970, pages 88 to SUMMARY OF THE INVENTION The present inventionemploys a plurality of light emitting diodes mounted on edge on atransparent insulating plate arranged in a desired design with eachdiode forming a segment of the design. Conductive leads to the ohmiccontacts of the diodes are formed either directly on the transparentplate or on an opaque layer overlying one surface of the plate, therebeing a window provided through the opaque layer for each diode. Aninsulating layer covers the conductive leads. 1r shape bridgeconnections have their legs extending through the insulating layer toconnect an ohmic contact with its associated lead. A further protectivelayer then covers the upper surface of the assembly. Preferably, areflective sheet is formed in the assembly above the diode edge oppositethe window through which light is emitted. If a visible indication isdesired from both sides, the reflective sheet may be omitted and awindow formed through the assembly above the upper edge of the diode.

In an alpha-numerical display device of the present invention the widthof the light emitting diodes determines the width of the lines definingthe segments of the design. This enables an extremely fine line patternto be obtained.

It is an object of the present invention to provide a novelalpha-numerical display device employing a light-emitting diode for eachsegment of the display.

It is a further object of the present invention to provide analpha-numerical display device employing light-emitting diodes having anovel integrated circuit connecting the ohmic contacts of the variousdiodes.

It is still another object of the present invention to provide a novelalpha-numerical display device employing a fine line light source foreach indicating line of the device.

It is another and further object of the present inven-' tion to providea novel alpha-numerical display device having a high degree ofbrightness.

A still further object of this invention is to provide a novelalpha-numerical display device which is economical to manufacture andwhich is rugged and reliable in use.

Another object of the present invention is to provide a novelalpha-numerical display device which provides an indication on bothsides.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric diagrammaticview of a light emitting diode as employed in the present invention.

FIG. 2 is a plan view of the upper surface of the transparent plateafter the conductive leads have been formed thereon.

FIGS. 3, 4, 6, 7, 9, 10 and 11 show in a sequence of diagrammatic.sectional views the formation of an alpha-numerical display deviceembodying a preferred form of the present invention.

FIG. 5 is a plan view of the transparent plate, the conductive leads andan insulating layer after the latter has been laid down on the former.

FIG. 8 is a diagrammatic plan view showing the location of the rr-shapejumpers of the assembly.

FIG. 12 is a diagrammatic plan view of the under (front) surface of oneunit of an alpha-numerical display device.

FIG. 13 is a diagrammatic plan view similar to FIG. 2 but showing amodified type of conductive leads.

FIG. 14 is a diagrammatic plan view similar to FIG. 5 showing theinsulating layer arrangement of the modified form.

FIG. 15 diagrammatically shows how the conductive strips areelectrically connected to the ohmic contacts of the light-emittingdiodes.

FIG. 16 is a diagrammatic illustration of one form of light emittingdiode.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 of thedrawings, there is shown therein a light-emitting diode .1 having a P-Njunction formed between a P-type region 2 and an N-type region 3. Thisdiode is preferably made, for example, of gallium phosphide, siliconcarbide or gallium nitride. The diode 1 is preferably made by cutting asemiconductor wafer with a diamond saw. Ohmic contacts 4 and 5 are andforms of the conductive strips 6.

3 formed on the P-type and N-type regions 2 and 3 respectively.

By way of example, and not by way of limitation, it

has been found that the following dimensions for the diode areparticularly effective. The thickness dimension a of the P-type regionis preferably 50 to 100 microns with 80 microns being particularlysuitable. The

thickness dimension b of the N-type region is preferably between 200 and300 microns with 250 microns being particularly suitable. Themaximum'thickness di- .mensions c and d of the ohmic contacts arepreferably of the'order of 1,000 Angs'troms. The length dimension e ofthe light emitting diode is preferably approximately 2 milimeters. Thewidth dimension f is preferably approximately 50 to l microns.

To understand the structure of the alpha-numerical I display device ofthe present invention, the progressive steps of forming a preferredembodiment thereof are shown in FIGS. 2 to 11, inclusive. As shown inFIGS.

face of the device. On the back or upper surface of this glass plate 7 aplurality of conducting strips 6 are formed as shown in'FlG. 2. Thesestrips 6 will provide sensitive resins are disclosed in detail inco-pending application, Ser. No. 227,444, filed Feb. 18, 1972 by thesame inventoL One of the mask windows 9 is u'sedfor indicating a decimalpoint and the others are used for a numeric indication. The layer 11 isformed by'first to form a protectivemask 16 for sand-blasting and havinga plurality of windows 17 as shown in FIG. 7.

Thereafter, a conductive resin layer 18 is formed on the protective mask16 and into the windows 17. As will hereafter be apparent, thisconductive resin layer 18 provides the jumper connections between theohmic contacts of the light emitting diodes l and the conductive strips6 and may be conveniently thought of as being 11' shaped.

The conductive resin layer 18 may be formed by coating a resin such asOI- MEX AG (Trade name of Pransene Co. Institute) or EPOTEK I-I-3l(Trade name) and heating at approximately 100C for 'about3 2 and 3, atransparent glass plate 7 provides the front;

hours. g

On the conductive layer 18 a protectivemask layer 19 is formedselectively as shown in FIG. 8. The protective mask layer 19 may beformed by coating a photo sensitive resin such as SONNE KPM 1027, thenexposing it through a mask having a predetermined patv tern, anddeveloping it. In order to provide the desired 1r shaped jumpers, theconductive resin layer 18 is selectively removed by sand-blasting asindicated by the arrowsinFIG. 9. i

A protective layer '20 is formed on the protective mask layers 16and 19to obtain a flat back (upper) surface as shown in FIG. 10. Theprotective layer 20 may be formed by coating aphoto sensitive resin suchas SONNE KPM 1027 and exposing it.

A protective plate 21- made by the same material as insulating plate 7is adhered to theprotective' layer 20 by an adhesive 22. A metal layer23 may beformed on an inner surface of the-layer 21 so that light fromthe I the trade name "fsONNE RPM 1027" and SONNE I KPM'10I8. which iscolored by a dye so as to be opaque to light from thelightemittingdiode. Photo laying down a layer 10 of a photo sensitive resin such 1 asSONNE KPM 1027. as shown in FIG. .3. This photo sensitive resin may becolored by a dye to be opaque to light from the diode; The photosensitive resin 10 is selectively exposed to light through an opticalmask not shown) having aipredeterminedpattern the insulating layer 11 asshown in FIGS. 4 andS.

This insulating layer 11 has eight positioning windows 12 (FIG. 5) forreceivingand holding the light emitting diode therein and a plurality ofIeadconnecting windows '13 located above predetermined portions Aphotosensitiveresin 14, such as SONNE KPM I027 is poured into thepositioning windows 12 and the light emitting diodes 1 are positionedtherein by exposing the resin 14 to light through mask windows 9 anddeveloping it to remove excess resin. The photo sensitive'resin 14 mayinclude a transparent powder for diffusinglight from the diode 1. Such atransparent powder may be selected from acrylic resin, glass, silica orpigmentpowders which are transparent to light from the diode l buthaving a different refractive index from that of the photo sensitiveresin 14. A photo sensitive resin 15 is coatedas shown in FIG. 6, andisthen selectively removed by exposing and developing processes diode, leffectively emits rto the outside through the window 9 andthe insulatingplate. 7 as shown in FIG. I

l l". FIG..12 shows a front view of: the insulating alphanumericaldisplay device 24 of this invention. The P-N junctions of the diodes'tlare faced 'on the insulating plate 7 so that light from the P-Njunctions effectively emits to the outside through the plate 7. It willbe appreciated that the maximum width of the numerical segments isdetermined by the thickness of the semiconductor wafer producing thelightemitting idiodes. For this reason, the width of the'alpha-numericaldisplay segment is freely selectable to provide a semicon,-. ductorwafer of various thicknesseswithout difficulty of coating or slicing. iI

' FIGS. 13 to 15 show a modified form invention. Referring first to FIG.13, a plurality of conductive strips 31 are laid'down'on a transparentglass plate 32by selective disposition. In this embodiment theconductive strips 31 are formed wider than the con- I ductivestripsshown in" FIG. 2 so that these conductive strips 31 themselves maybe: used as a mask for preventing unwanted light frottrthelight emittingdiodes.

Thereafter, an insulating layer 33 (FIG. '14) which has been colored bya blue dye is formed on the glass plate 32. This insulating layer 33 hasfour windows 34 which are positioning portions for the light emittingdiodes 35. Nine ofthese light emitting diodes having the sameconstruction as shownin FIG. 1' are'securedto the glass plate 32 by anadhesive or a photo sensitive resin exposed from the glass plate side.This particular process is not essential to this invention, but isuseful to prevent I the P-N junctions from having a conductive resinflowing between thediodes 35 and the plate 32. The N 1 of the present Ijunctions of the diodes 35 are positioned perpendicular to the plane ofthe glass plate 32.

Thereafter, a conductive resin or a silver paint is poured into thewindows 34 and heated to form conductive layers 36 for electricallyconnecting the ohmic contacts of the diodes 35 to the conductive strips31 respectively so that an alpha-numerical display device 37 is obtained(FIG.

The alpha-numerical display device 37 may be coated with a protectiveresin to prevent deterioration of the diodes 35.

In the preferred embodiments, an indication is viewed through thetransparent insulating plate 7 or 32 but it should be noted that it ispossible to have light also emitted from the back side provided a windowis left on the back side from the light emitting diode outwardly to therear.

The insulating plate 7 or 32 may be colored and may be transparent onlyto light from the diode so that the contrast for indication is improved.

I claim as my invention:

1. An alpha-numerical display device comprising a transparent insulatingplate having a plurality of light emitting diodes mounted thereon withtheir P-N junctions disposed perpendicular to the plane of said plateand arranged in an array for alpha-numerical display, and means forselectively forwardly biasing different ones of said light emittingdiodes, a plurality of conducting strips are formed on the same surfaceof said transparent insulating plate as said diodes and in which a firstinsulating layer is formed on said plate between said strips except fora window therethrough opposite each light emitting diode and light isemitted from said diode in a direction parallel to said P-N junction.

2. An alpha-numerical display device according to claim 1, in which asecond insulating layer is formed over said conducting strips and saidfirst insulating layer and conductive jumpers formed on said secondinsulating layer and extending down therethrough and each having twoterminal arms, one of which is connected to one side of said diode andthe other to a conductive strip.

3. An alpha-numerical display device according to claim 1, in which saidfirst insulating layer is opaque.

4. An alpha-numerical display device comprising a transparent insulatingplate having a plurality of light emitting diodes mounted thereon withtheir P-N junctions disposed perpendicular to the plane of said plateand arranged in an array for alpha-numerical display, and means forselectively forwardly biasing different ones of said light emittingdiodes, in which said means for forwardly biasing includes a pluralityof conducting strips mounted 'on the same surface of said transparentinsulating plate as said light emitting diodes, an insulating layersubstantially covering nearly all of the area between said conductingstrips, whereby said insulating layer and strips act as an opaque maskand light emitted from said diodes in a direction parallel to said P-Njunctions.

5. An alpha-numerical display device comprising a transparent insulatingplate, a plurality of light emitting diodes mounted in a pre-arrangeddesign on one surface of said plate and having P-N junctions normal tosaid plate, a plurality of conductive strips formed on said plate on thesame side that said diodes are mounted, a first layer of opaqueinsulating material,

through said second insulating layer into contact with one of saidconductive strips and light emitted from said diodes in a directionparallel to said P-N junctions.

6. An alpha-numerical display device according to claim 5, in which aprotective insulating layer covers the assembly over the side oppositesaid transparent insulating plate.

7. An alpha-numerical display device according to claim 5 having areflecting member for each of said diodes mounted above and spaced fromsaid diodes to reflect light through said window.

8. An alpha-numerical display device according to claim 5, in which asecond window is provided on the back side of the array for each of saiddiodes, whereby when light is emitted from said diodes it may be seenfrom both sides of the display device.

9. An alpha-numerical display device according to claim 2, in which saidconducting strips extend out beyond at least one edge of said secondinsulating layer to provide terminal connections for said conductingstrips.

10. A light emitting device comprising an insulating plate, at least twoconductive layers formed on said plate, an insulating layer formed onsaid plate and having at least one window, a light emitting diodepositioned in said window, said light emitting diode having twoelectrodes and a P-N junction perpendicular to a plane of saidinsulating plate, and means for connecting said electrodes to saidconductive layers respectively.

11. A light emitting device according to claim 10, wherein saidinsulating plate is transparent to light from said light emitting diode.

12. A light emitting device according to claim 10, wherein saidconnecting means are conductive resin layers formed between saidelectrodes and said conductive layers respectively.

13. A light emitting device according to claim 10, wherein said windowof said insulating layer has a portion for positioning said lightemitting diode and a portion for receiving said connecting means.

14. A light emitting device comprising an insulating plate, a pluralityof conductive layers formed on said insulating plate, an insulatinglayer formed at least on said insulating plate and having a plurality ofwindows, a plurality of light emitting diodes positioned in said windowsrespectively with P-N- junctions normal to said plate, said insulatinglayer absorbing at least light from said light emitting diode, saidlight emitting diodes having two electrodes and a junction perpendicularto a plane of said insulating plate, and means for connecting saidelectrodes to said conductive layer, respectively.

1. An alpha-numerical display device comprising a transparent insulatingplate having a plurality of light emitting diodes mounted thereon withtheir P-N junctions disposed perpendicular to the plane of said plateand arranged in an array for alphanumerical display, and means forselectively forwardly biasing different ones of said light emittingdiodes, a plurality of conducting strips are formed on the same surfaceof said transparent insulating plate as said diodes and in which a firstinsulating layer is formed on said plate between said strips except fora window therethrough opposite each light emitting diode and light isemitted from said diode in a direction parallel to said P-N junction. 2.An alpha-numerical display device according to claim 1, in which asecond insulating layer is formed over said conducting strips and saidfirst insulating layer and conductive jumpers formed on said secondinsulating layer and extending down therethrough and each having twoterminal arms, one of which is connected to one side of said diode andthe other to a conductive strip.
 3. An alpha-numerical display deviceaccording to claim 1, in which said first insulating layer is opaque. 4.An alpha-numerical display device comprising a transparent insulatingplate having a plurality of light emitting diodes mounted thereon withtheir P-N junctions disposed perpendicular to the plane of said plateand arranged in an array for alpha-numerical display, and means forselectively forwardly biasing different ones of said light emittingdiodes, in which said means for forwardly biasing includes a pluralityof conducting strips mounted on the same surface of said transparentinsulating plate as said light emitting diodes, an insulating layersubstantially covering nearly all of the area between said conductingstrips, whereby said insulating layer and strips act as an opaque maskand light emitted from said diodes in a direction parallel to said P-Njunctions.
 5. An alpha-numerical display device comprising a transparentinsulating plate, a plurality of light emitting diodes mounted in apre-arranged design on one surface of said plate and having P-Njunctions normal to said plate, a plurality of conductive strips formedon said plate on the same side that said diodes are mounted, a firstlayer of opaque insulating material formed on said plate between saidstrips except for windows in which said diodes are located, a secondinsulating layer covering said first opaque insulating layer and saidconductive strips, bridging strips formed on said second insulatinglayer, each bridging strip having one end thereof extending down throughsaid second insulating layer into contact with a terminal of said diodeand having the other end thereof extending down through said secondinsulating layer into contact with one of said conductive strips andlight emitted from said diodes in a direction parallel to said P-Njunctions.
 6. An alpha-numerical display device according to claim 5, inwhich a protective insulating layer covers the assembly over the sideopposite said transparent insulating plate.
 7. An alpha-numericaldisplay device according to claim 5 having a reflecting member for eachof said diodes mounted above and spaced from said diodes to reflectlight through said window.
 8. An alpha-numerical display deviceaccording to claim 5, in which a second window is provided on the backside of the array for each of said diodes, whereby when light is emittedfrom said diodes it may be seen from both sides of the display device.9. An alpha-numerical display device according to claim 2, in which saidconducting strips extend out beyond at least one edge of said secondinsulating layer to provide terminal connections for said conductingstrips.
 10. A light emitting device cOmprising an insulating plate, atleast two conductive layers formed on said plate, an insulating layerformed on said plate and having at least one window, a light emittingdiode positioned in said window, said light emitting diode having twoelectrodes and a P-N junction perpendicular to a plane of saidinsulating plate, and means for connecting said electrodes to saidconductive layers respectively.
 11. A light emitting device according toclaim 10, wherein said insulating plate is transparent to light fromsaid light emitting diode.
 12. A light emitting device according toclaim 10, wherein said connecting means are conductive resin layersformed between said electrodes and said conductive layers respectively.13. A light emitting device according to claim 10, wherein said windowof said insulating layer has a portion for positioning said lightemitting diode and a portion for receiving said connecting means.
 14. Alight emitting device comprising an insulating plate, a plurality ofconductive layers formed on said insulating plate, an insulating layerformed at least on said insulating plate and having a plurality ofwindows, a plurality of light emitting diodes positioned in said windowsrespectively with P-N junctions normal to said plate, said insulatinglayer absorbing at least light from said light emitting diode, saidlight emitting diodes having two electrodes and a junction perpendicularto a plane of said insulating plate, and means for connecting saidelectrodes to said conductive layer, respectively.